User Manual

MM102365V1 Rev. B
The Network Access Router connection (a T1 Point-to-Point microwave link) terminates at the Operation
Center.
3.3 SUB-SYSTEM COMMUNICATION LINKS
The ISM radio is a Direct Sequence Spread Spectrum (DSSS) radio compliant with the FCC Part 15.247
regulations. It operates in the unlicensed ISM frequency band available for public use, between 2.400-
2.4835 GHz.
The radio operates as a subsystem within the OpenSky network to provide point-to-multipoint
communication links between tower sites and cell sites.
The ISM link extends a tower site’s coverage area beyond the devices it can reach directly. Areas poorly
served by high profile tower sites due to budgetary constraints, remote location or topographical
challenges can be affordably and reliably served from a cell site with optional ISM repeater site(s) in an
ISM subsystem.
3.4 RADIO OPERATING MODES: MASTER AND SLAVE
The ISM radio can be configured to operate in either of two modes: Master or Slave.
3.4.1 Master
A radio in Master mode controls the RF communications path of up to six radios configured in Slave
mode. A Master operating in Time Division Multiplexed (TDM) order initiates all RF communications.
In short, the Master radio addresses all associated Slave radios in round-robin fashion, giving each in turn
the opportunity to transmit or receive ISM addressed voice and data packets.
3.4.2 Slave
A radio in Slave mode transmits and receives segmented IP packets encapsulated with ISM headers only
when addressed by its associated ISM Master radio. The Slave radio buffers data received from its SLIP
(or fiber optic) interface until granted the time slot to transmit to its respective Master. A Slave radio has a
maximum amount of data that is transmitted in any given time slot provided by the Master.
NOTE
It should be noted that an ISM Master radio is also capable of communicating with
another ISM Master radio depending on the system design.
3.5 ISM NETWORK CONFIGURATION
Figure 3-1 shows an ISM Tower Top radio supporting six cell site ISM radios. In this configuration, the
tower site is equipped with several DCX Base Station Units and a Backhaul Router with a single Master
ISM radio acting as a hub.
15